What is CLS?

Let Publisher Collective explain...

So what is CLS?

Cumulative Layout Shift, also known as CLS, is a part of Google’s Core Web Vitals. It is the measurement of layout shifts that can take place on a webpage as it not only loads, but also as it’s engaged and interacted with. 

Layout shifts are often the result of several different elements housed within a webpage that all decide to load up at different times, and can often lead to a sense of pure frustration and an exaggerated eye roll from the user before they inevitably leave the site. Not ideal. 

What this can look like is anything from text moving, font size changing, and pop-ups that can move around the page, causing your eyes to twitch slightly as they track the movement, or your thumb to tap the wrong link when you’re on your phone.

Core Web Vitals

Long gone are the days when your site could simply match the search intent of a user; in the summer of 2021, Google included three Core Web Vitals that would play a part of the Page Experience ranking – CLS being one of them. CLS has the least impact on the overall Core Web Vital score and is the easiest to fix! We break this down in a previous blog here, but the point is, if your site hasn’t applied best practices, you’ll be moved to the dreaded page 2 of search. Eek.

Checking your CLS score

We recommend using the online service Page Speed Insights – in addition to Google Search Console – as it will give you a better view of your scores overtime.

What’s considered a good CLS score?

Google uses the figures below to measure a “good” amount of CLS. Measurements start at zero – indicating no CLS at all – and can increase to any positive number. As you can see, it doesn’t take much movement on the page for Google to consider it an issue:

  • Good CLS: Below 0.10
  • Needs improvement CLS: Between 0.10 and 0.25
  • Poor CLS: Above 0.25

What affects your CLS score?

A few things can be the culprits – often it’s something from the list below, so ensure you’re frequently checking for these issues as you start to test: 

  • Dimensionless images and SVGs
  • Speed loading fonts
  • Embeds and iFrames
  • Ads with multiple demand sizes

That’s where Publisher Collective comes in. Our Astroboard is a floating unit, which means it lays over the page rather than within it.  Meaning it can never actually move any content on your page as it isn’t placed within it, causing no adverse effects to other elements on the page and cuts down on CLS. With this technology, you can implement high-impact large-format ads without negatively affecting your pages’ performance or ranking.